# 全部变量练习
a = 1


def test1():
    a = 2
    print(a)


def test2():
    print(a)


# 在函数内部修改全局变量的值
def test3():
    global a
    a = 3
    print(a)


def test4():
    print(a)


test1()
test2()
test3()
test4()
